History of Ideas of Motion

1. History of Ideas of Motion

2. Aristotle, Copernicus, Galileo

3. Aristotle’s laws of motionNatural Motion on Earth • Questions he asked: • Why do objects move the way they do on earth? • Why do objects fall when dropped? • Why do bubbles rise in water? • His answer: Objects move to reach their natural state- rest. • Different elements move differently • Earth towards the center of the earth • Fire away from center of the earth • Water and air occupy the in between space • Motion is linear – Natural motion is up and down

4. Aristotle’s laws of motionNatural Motion of the Heavens • Objects on Earth move by natural motion either up (to the heavens) or down (to the Earth). • Objects in heavens (above moon) move in circles • Why? Universe finite – linear motion would force objects to fall off the end of universe, so they move in circles.

5. Aristotle’s laws of motionViolent Motion • Violent motion does not occur naturally. • If an object is in motion, other than natural motion, then there must be some force that is responsible for that motion. • When that force stops the motion stops. • “Being at rest" was the natural state of motion of any object. • The Earth (in it’s natural state) is at rest.

6. Aristotle’s Universe Planets on physical spheres – each moving the other – earth and sphere of prime mover stationary

7. Aristotle and the Church

8. Next came Copernicus(1473-1543) • Central European, mathematician, astronomer, physician, governor, soldier, etc. • Formulated heliocentric theory of the universe

9. The Copernican Model (1530 A.D.)(Explaining Retrograde Motion) • Because the planets are in the heavens, they must move in perfect circles at a constant speed. But … • The Earth is not at the center of the planetary system (i.e., the universe). Only the Moon goes around the Earth. • The Sun is at the center of the planetary system. • Compared to the distance of the fixed stars, the distance from the Earth to the Sun is negligible. • The daily revolution of the sky is due to the Earth’s rotation. • The Sun’s annual motion is due to the Earth’s orbit around the Sun. • Retrograde motion is due to the Earth’s orbit around the Sun.

10. The Copernican Model (1530 A.D.) (Explaining Retrograde Motion) Retrograde motion is explained by the Earth “passing” (or being passed by) another planet in its orbit.

11. And finally there’s Galileo(1564-1642) • Galileo studied the writings of Copernicus and did experiments – lots of them. • He was the first person to do scientific experiments • Father of modern science

12. Galileo’s Experiments Dropping balls to measure gravity Rolling balls to examine inertia Observing the sky through a telescope

13. What Galileo Saw • An imperfect Sun (sunspots)

14. What Galileo Saw • An imperfect Sun (sunspots) • A Moon with mountains and craters

15. What Galileo Saw • An imperfect Sun (sunspots) • A Moon with mountains and craters • The “ears” of Saturn

16. What Galileo Saw • An imperfect Sun (sunspots) • A Moon with mountains and craters • The “ears” of Saturn • Four moons orbiting Jupiter

17. What Galileo Saw • An imperfect Sun (sunspots) • A Moon with mountains and craters • The “ears” of Saturn • Four moons orbiting Jupiter • The phases of Venus